Time-activity curves of 11C-SA4503-derived radioactivity in tumour, brain and blood pool. Solid line: animals scanned after short pentobarbital anaesthesia (< 20 min, control condition, n = 5); dotted line: same animals scanned after protracted pentobarbital anaesthesia (>3.5 h, n = 5). The PET data were normalized to a body weight of 330 g and an injected radioactivity dose of 20 MBq, as described previously [24]. The effect of protracted anaesthesia on brain uptake (after >10 min) and tumour uptake (after >20 min) was statistically significant, in contrast to the effect on radioactivity in the blood pool